4) Some publishers really care about theme (like Brian) so you’ll get more opportunities if your game has one. You’ll get in the door. Theme sells better than math. Games are an experience, and theme tells your story.

3) A themed games is more interesting to players so you’ll get more playtesters. It shows your playtesters that you respect their time and level of enjoyment.

2) Save the publisher time by showing them it is complete. A game with no theme isn’t done yet and they would usually not do that work if they can avoid it. Once you’re in the door, you’re more likely to stay there.

1) Theme is part of the design. Why are we even talking about them as if they are independent parts?